Wobble piston and cylinder arrangement

Abstract

A wobble piston usable in a cylinder comprising one or both of the confronting surfaces of wobble piston head or valve plate being convexly curved in the plane of the wobble motion and being straight in a plane that is transverse to the plane of the wobble motion.

We claim: 
     
       1. In a piston head for a wobble piston usable in a cylinder having a flat upper end, the improvement wherein: the upper surface of the piston head is curved convexly in the plane of the wobble motion of the piston and is straight in a plane that is transverse to the plane of the wobble motion.   
     
     
       2. A piston head in accordance with claim 1 wherein the curve is a third order polynomial. 
     
     
       3. A piston head in accordance with claim 1 wherein the curve is formed as the arc of two identical circles the centers of which are equally offset from the longitudinal centerline of the piston, and the curve approximates a third order polynomial. 
     
     
       4. In a fluid pumping apparatus having a cylinder with a flat valve plate forming the top end of the cylinder and a wobble piston with a piston head operating in the cylinder and a piston rod mounted to move in a plane normal to the valve plate, the improvement wherein: the top surface of the piston head is curved convexly in the plane of the motion of the piston rod and is straight in a plane transverse to said plane of motion.   
     
     
       5. An apparatus in accordance with claim 4, wherein the curve of the top surface approximates the locus of all points of the top surface that are nearest to the valve plate as the piston rod moves through said plane of motion. 
     
     
       6. An apparatus in accordance with claim 4, wherein the curve approximates a third order polynomial. 
     
     
       7. A wobble piston, comprising: a piston rod;   a piston head fixed to the piston rod;   a cup seal mounted on the head; and   a cup retainer securing the cup seal to the piston head, the retainer having a top surface that is curved convexly in one plane and straight in the plane transverse to the one plane.   
     
     
       8. A wobble piston in accordance with claim 7, wherein the curve of the top surface approximates a third order polynomial. 
     
     
       9. In a fluid pumping apparatus having a cylinder with a valve plate forming the top end of the cylinder and a wobble piston with a piston head operating in the cylinder and a piston rod mounted to move in a single plane, the improvement wherein: the surface of the piston head that confronts the valve plate is flat and the surface of the valve plate that confronts the piston head is curved convexly in the plane of the motion of the piston rod and is straight in a plane transverse to said plane of motion.   
     
     
       10. An apparatus in accordance with claim 9, wherein the curve of the surface of the valve plate approximates the locus of all points of the surface that are nearest to the piston head surface as the piston rod moves through said plane of motion. 
     
     
       11. An apparatus in accordance with claim 9, wherein the curve approximates a third order polynomial. 
     
     
       12. In a fluid pumping apparatus having a cylinder with a valve plate forming the top end of the cylinder and a wobble piston with a piston head operating in the cylinder and a piston rod mounted to move in a single plane, the improvement wherein: the surfaces of the valve plate and piston head that confront each other are straight in a plane transverse to the plane of motion of the piston rod and one or both of the surfaces are curved convexly in the plane of the motion.